Need help with A/C system

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

91v2500

Junior Member
Joined
Mar 22, 2020
Posts
28
Reaction score
7
Location
Washington DC
First Name
Korey
Truck Year
1991
Truck Model
2500
Engine Size
5.7
My a/c compressor stays on as long as the truck is running. I have all new parts except the condenser, also there’s no cold air blowing on the inside only heat and it’s blows low pressure
 

Bextreme04

Full Access Member
Joined
May 13, 2019
Posts
4,445
Reaction score
5,586
Location
Oregon
First Name
Eric
Truck Year
1980
Truck Model
K25
Engine Size
350-4bbl
My a/c compressor stays on as long as the truck is running. I have all new parts except the condenser, also there’s no cold air blowing on the inside only heat and it’s blows low pressure

Do you know anything about AC systems?

The AC clutch should only be engaged when the HVAC lever inside is set to an AC setting or defrost. The HVAC controls trigger a relay mounted on the evaporator housing in the engine bay. If the compressor is always on, you either have a short somewhere in that system or the compressor clutch is seized. If the compressor is engaged and you don't have cold inside, you either have the blend door not functioning or the AC is not properly charged. There's a bunch of troubleshooting you can do to determine what is exactly wrong, but it can get pretty involved especially if you aren't familiar with how AC works.
 

tadslc

Full Access Member
Joined
Jan 20, 2020
Posts
120
Reaction score
134
Location
Birmingham, AL
First Name
Tad
Truck Year
1981
Truck Model
C10
Engine Size
350 Blueprint
I replaced some A/C components earlier this year for the first time. Much more to it than I first thought but there is a ton of information on the internet to help you along.
Ended up working great, much to my surprise. It's quite doable for someone that's never dealt with A/C before, just take your time and do your research.
 

91v2500

Junior Member
Joined
Mar 22, 2020
Posts
28
Reaction score
7
Location
Washington DC
First Name
Korey
Truck Year
1991
Truck Model
2500
Engine Size
5.7
Thanks for the replies and information
@bextreme I’m some what familiar with the hvac system but I think you’re right it maybe a short somewhere
 

Bextreme04

Full Access Member
Joined
May 13, 2019
Posts
4,445
Reaction score
5,586
Location
Oregon
First Name
Eric
Truck Year
1980
Truck Model
K25
Engine Size
350-4bbl
Thanks for the replies and information
@bextreme I’m some what familiar with the hvac system but I think you’re right it maybe a short somewhere
I just wanted to make sure you had at least basic familiarity. I would start by going onto the Resource Library forum on here and download the service manual and electrical schematics for your truck.

Then I'd start hunting down why the compressor is engaged all the time.

Once you get it to engage and disengage when it is supposed to, then you can try to figure out why it isn't cooling. You will likely need to rent or borrow a set of AC gauges from a local parts store for checking refrigerant charge and pressures if you figure out the electrical issue and still dont have cold air.
 

91v2500

Junior Member
Joined
Mar 22, 2020
Posts
28
Reaction score
7
Location
Washington DC
First Name
Korey
Truck Year
1991
Truck Model
2500
Engine Size
5.7
Thanks I’ll look into it
 

91v2500

Junior Member
Joined
Mar 22, 2020
Posts
28
Reaction score
7
Location
Washington DC
First Name
Korey
Truck Year
1991
Truck Model
2500
Engine Size
5.7
Just an update it was the blend door that broke and the new temperature control unit was malfunctioning
 

91v2500

Junior Member
Joined
Mar 22, 2020
Posts
28
Reaction score
7
Location
Washington DC
First Name
Korey
Truck Year
1991
Truck Model
2500
Engine Size
5.7
Thanks all for the help
 

Latest posts

Forum statistics

Threads
44,204
Posts
951,598
Members
36,338
Latest member
jmoe
Top